Mining and Processing
Mining has historically been completed using room and pillar and long hole open stoping. All phases of mining, except haulage to surface, are carried out by La Negra personnel and the union, with surface haulage managed by a local contractor. Planned stopes are longitudinal, approximately 20 metres high by 20 metres long by 6 metres wide. The mine does not employ systematic backfilling, waste rock is either utilized at surface or placed in inactive stopes. Ground support requirements are minimal due to generally competent rock conditions. The mine is currently operating at a production rate of 55% of its 2,500 tpd capacity.
The processing facility at Minera La Negra consists of a standard crushing, grinding, flotation, and filtration circuit producing lead-silver, copper-silver, and zinc concentrates (in that order). Crushing is completed using a primary jaw crusher with secondary and tertiary cone crushers, followed by two parallel ball milling lines for grinding. Flotation circuit is three stages to recover the different concentrates. The processing plant flowsheet has been well established and is little changed over the history of the operation, allowing for operating parameters and recoveries to be well understood.
In addition to the statutory government royalties, there are two distinct royalties on the property:
- Peñoles - 2.8%, subject to certain deductions.
- Orion - 2.5% royalty.